Exchange - Mutiple Email Accounts, Two domains, two servers, do different companies

I have a user (we will call him Craig) who currently has 1 exchange account. I have been asked to add an email account from another exchange account (different server, different domain, my sister company) One is on Domain A and one is on Domain B. Domains A & B are on separate, fire-walled networks. These domains exist at two different facilties.

Craig would have accounts on both networks and does work with people in Domain A and Domain B.

In theory, the best option would be that both sets of emails are delivered to one inbox, and when he replies, Exchange knows which account the email was delivered from and would send from that account.

Unfortunately, I am the IT person at one of the companies, and not both, so I only have access to my Active Directory and Exchange Server, but I'm sure I can get the settings needed for the other server to set up.

I think that if you only have access to your domain, the easy method to get it working is to create a new user account to craig to access resources in the other domain. When a server ask for credential to access resources in the other domain, craig only have to give the credential for this new account.

For email, I suggest to use only one account with craig profile in Outlook or some other email client. For this in the other domain, an administrator could create a contact object to the email account for craig in your domain. For example craig@yourdomain.com. Then create a mailbox for craig in the ohter domain and set up a forward for this other domain to the contact created for your domain. This way craig will recieve both emails in one exchange server.

so the email would come from his account, on one domain to another account on another domain. so he couldn't hit "reply" because he would be replying to himself, in a sense. . .

you would think Exchange would have a better option, but everything I have read, there really isn't a solution. I could set up to exchange accounts on his computer, but he would have to login to each one seperately (as long as outlook anywhere) that may work? But it would suck to have to login to each one seperately.

Your computer can not belong to two domains. You can configure the computer and the user for only one domain. You can configure two outlook profiles to open 2 exchange servers in every profile. You can make this in control panel - users - mail. You don't have to create two profilesin the computer, because the computer only can belong to one domain. The other domain has to be access using a script or something like it. Maybe using net use command.

For example

Net use \\server\share /user:otherdomain\username
and it will prompt for password

The email solution could be configure both mailboxes. Maybe your domain like exchange server and the other like pop account. This both can be accessed by one profile in Outlook, you can configure rules in outlook to send pop account to a pst in the computer and the exchange account will be in an ost file. Then you can send a email and select for wich account you whant to send.

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Note: If you make a forward for the otherserver, the user will receive the emails send to the otherdomain in your exchange server and he can reply to this email without any problem, but the email will be sent with your account domain. (If you look at the emails forwarded they says sent from anotherpeople@otherdomain.com, not craig@anotherdomain.com